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Results for “synergistic effect”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

The synergistic effects of slip ring-brush design and materials

The design, fabrication, and subsequent testing of four power slip rings for synchronous orbit application are described. The synergistic effects of contact materials and slip ring-brush design are studied by means of frequent and simultaneous recording of friction, wear, and electrical noise. Data generated during the test period are presented along with post test analysis data.

Lewis, N. E.↗
NASA NTRS2009

Summary of the Synergistic Effects Obtained by the Present Study of Vortical Flows

This chapter identifies the benefits that occurred to the AVT-113 task group members and the resulting progress made to two separate vortical flow proposals for task group status being combined into one. Both of these proposals dealt with multiple-vortices, and though they shared different focuses, the general topic, as well as the specific features of this flow, made it of great interest to each sub-task or facet member. The joint meetings increased our overall understanding of vortical flow and the synergistic benefits are summarized in terms of experimental and computational data, virtual laboratory usage, dissemination of results, and career development.

Lamar, John E.↗
NASA NTRS1992

Synergistic effects of ultraviolet radiation, thermal cycling, and atomic oxygen on altered and coated Kapton surfaces

The photovoltaic (PV) power system for Space Station Freedom (SSF) uses solar array blankets which provide structural support for the solar cells and house the electrical interconnections. In the low Earth orbital (LEO) environment where SSF will be located, surfaces will be exposed to potentially damaging environmental conditions including solar ultraviolet (UV) radiation, thermal cycling, and atomic oxygen. It is necessary to use ground based tests to determine how these environmental conditions would affect the mass loss and optical properties of candidate SSF blanket materials. Silicone containing, silicone coated, and SiO(x) coated polyimide film materials were exposed to simulated LEO environmental conditions to determine there durability and whether the environmental conditions of UV, thermal cycling and oxygen atoms act synergistically on these materials. A candidate PV blanket material called AOR Kapton, a polysiloxane polyimide cast from a solution mixture, shows an improvement in durability to oxygen atoms erosion after exposure to UV radiation or thermal cycling combined with UV radiation. This may indicate that the environmental conditions react synergistically with this material, and the damage predicted by exposure to atomic oxygen alone is more severe than that which would occur in LEO where atomic oxygen, thermal cycling and UV radiation are present together.

Dever, Joyce A.↗
NASA NTRS1992

Synergistic effects of ultraviolet radiation, thermal cycling and atomic oxygen on altered and coated Kapton surfaces

The photovoltaic (PV) power system for Space Station Freedom (SSF) uses solar array blankets which provide structural support for the solar cells and house the electrical interconnections. In the low earth orbital (LEO) environment where SSF will be located, surfaces will be exposed to potentially damaging environmental conditions including solar ultraviolet (UV) radiation, thermal cycling, and atomic oxygen. It is necessary to use ground based tests to determine how these environmental conditions would affect the mass loss and optical properties of candidate SSF blanket materials. Silicone containing, silicone coated, and SiO(x) coated polyimide film materials were exposed to simulated LEO environmental conditions to determine their durability and whether the environmental conditions of UV, thermal cycling and oxygen atoms act synergistically on these materials. A candidate PV blanket material called AOR Kapton, a polysiloxane polyimide cast from a solution mixture, shows an improvement in durability to oxygen atoms erosion after exposure to UV radiation or thermal cycling combined with UV radiation. This may indicate that the environmental conditions react synergistically with this material, and the damage predicted by exposure to atomic oxygen alone is more severe than that which would occur in LEO where atomic oxygen, thermal cycling and UV radiation are present together.

Dever, Joyce A.↗
NASA NTRS1972

The synergistic effects of slip ring-brush design and materials

The design, fabrication, and testing of four power slip rings for synchronous orbit application are considered. Environmental and instrumentation systems necessary for monitoring electrical noise, friction, and brush wear in air and at less than 5 X 10 to the minus 8th power torr were developed. Composite brushes consisting of silver-molybdenum disulfide-graphite and silver-niobium diselenide-graphite were employed on rings of coin silver and rhodium plate. These four contact combinations were tested during ambient condition run-in at 150 and a humidity sequence at 0.1. The first nine months of a two year vacuum test performed at 0.1 rpm were completed.

Lewis, N. E.↗
NASA NTRS1980

Synergistic effects in trace gas-aerosol interactions

The reaction of SO2 and NO2 with soot has been studied experimentally by gravimetric determination of chemisorption with subsequent analysis of the chemisorbed species by various techniques. When samples of commercially available carbon black (used as soot surrogate) are exposed to SO2 or NO2 in dry air or N2 as carrier gas, no quantitative chemisorption (less than 5 micrograms per mg of substrate) is observed. However, exposure of the same grade of carbon to a combination of SO2 and NO2 in dry air of N2 results in significant chemisorption (180-200 micrograms/mg), a major fraction of which is analyzed as sulfate.

Schryer, D. R.↗
NASA NTRS1981

Stratospheric ozone and temperature perturbations - An examination of synergistic effects

Experiments have been carried out to investigate the time-dependent effects of combined releases of CO2 and chlorofluoromethanes (CFM) on stratospheric ozone and temperature. The analysis also examines the effects of steady-state variations in CFM, CO2, and solar UV flux levels on surface temperature and latitudinal temperature distribution. Results indicate that ozone depletion, due to combined effects of CO2 and CFM increases, may show a local maximum of about 6% at about the time CO2 doubles (approximately 60 yr from now). After that, the downward trend in ozone due to Cl(x) catalytic destruction is reestablished and continues, reaching approximately 15% depletion. At steady state, compensation due to CO2 increases is approximately 1% for two to four times the ambient CO2 levels.

Callis, L. B.↗
NASA NTRS1999

Synergistic Effects of Physical Aging and Damage on Long-Term Behavior of Polymer Matrix Composites

The research consisted of two major parts, first modeling and simulation of the combined effects of aging and damage on polymer composites and secondly an experimental phase examining composite response at elevated temperatures, again activating both aging and damage. For the simulation, a damage model for polymeric composite laminates operating at elevated temperatures was developed. Viscoelastic behavior of the material is accounted for via the correspondence principle and a variational approach is adopted to compute the temporal stresses within the laminate. Also, the effect of physical aging on ply level stress and on overall laminate behavior is included. An important feature of the model is that damage evolution predictions for viscoelastic laminates can be made. This allows us to track the mechanical response of the laminate up to large load levels though within the confines of linear viscoelastic constitutive behavior. An experimental investigation of microcracking and physical aging effects in polymer matrix composites was also pursued. The goal of the study was to assess the impact of aging on damage accumulation, in ten-ns of microcracking, and the impact of damage on aging and viscoelastic behavior. The testing was performed both at room and elevated temperatures on [+/- 45/903](sub s) and [02/903](sub s) laminates, both containing a set of 90 deg plies centrally located to facilitate investigation of microcracking. Edge replication and X-ray-radiography were utilized to quantify damage. Sequenced creep tests were performed to characterize viscoelastic and aging parameters. Results indicate that while the aging times studied have limited ]Influence on damage evolution, elevated temperature and viscoelastic effects have a profound effect on the damage mode seen. Some results are counterintuitive, including the lower strain to failure for elevated temperature tests and the catastrophic failure mode observed for the [+/- 45/9O3](sub s), specimens. The fracture toughness for transverse cracks increases with increasing temperature for both systems: transverse cracking was completely absent prior to failure in [+/- 45/903](sub s), and was suppressed for [02/903](sub s). No significant effect of damage on aging or viscoelastic parameters was observed.

Brinson, L. Cate↗
NASA NTRSDate not supplied

Effect of Synergistic Space Effects on Properties of Novel Polymer Composite Materials (PCM)

Evaluate the long-term performance of composite materials in space by exposing them to the actual space environment and analyzing changes in their interfacial properties, using the International Space Station (ISS) and the MISSE for experimentation. This research could assist in the design of future spacecraft, assessing risk and enhancing safety and reliability of spacecraft structural materials for space exploration.

R Vaidyanathan↗
NASA NTRS2011

Identification of Cardiometabolic Vulnerabilities Caused by Effects of Synergistic Stressors that are Commonly Encountered During Space Missions

Microgravity is a physiologically challenging state even when at rest. Astronauts experience additional physical and mental stresses, such as prolonged exertion, sleep loss and circadian misalignment, that could impact cardiovascular function. The main goals of this four year NASA project are to characterize the independent and synergistic effects on cardiovascular and immune function of: (1) circadian misalignment; (2) sleep loss; and (3) varied physical and mental stressors, mimicking some of the synergistic stressors experienced by astronauts. Sixteen healthy volunteers, aged 35-55 years, will be studied with standardized behavioral stressors occurring across all circadian phases, both with and without accruing sleep loss, achieved via two 11-day "forced desynchrony" protocols performed in each subject (randomized, within-subject design), where wake periods are advanced 4-h each "day" (i.e. recurring 20-h "days"). One protocol permits 8.33 h sleep opportunity per 20-h "day" (=10 h sleep per 24-h), and the other permits 5 h sleep per 20-h "day" (=6 h sleep per 24-h; matching the reported sleep duration of astronauts). In both protocols, subjects will perform a standardized stress battery including a cognitively challenging task; bicycle exercise, and passive 60deg head up tilt. Outcome variables include blood pressure, heart rate, arrhythmia frequency, cardiac vagal tone (from heart rate variability), sympathetic activity (catecholamines), and endothelial function. Additional measures of cardiac function (echocardiography), responses to a passive 80deg head up tilt, maximal oxygen uptake, and immune function will be assessed at the beginning and at the end of each protocol (i.e., without and with sleep loss, and before and after circadian misalignment). We hope to identify the relative impact on cardiovascular risk markers of varied behavioural stressors while subjects experience circadian misalignment and sleep loss, mimicking some of the synergistic stressors experienced by astronauts. Supported by NASANNX1 OAR 1 OG.

Ruger, M.↗
NASA NTRS1990

Environmental interactions on Space Station

This paper describes the key environment/system interactions associated with the Space Station and its companion polar platform and defines the range of test environments that will need to be simulated. These environments include the neutral atmosphere, the ionospheric plasma, natural and man-made particulates, the ambient magnetic field, the South Atlantic Anomaly, and the ram/wake environment. The system/environment interactions include glow, oxygen erosion, drag, radiation effects, induced electric fields, high-voltage solar-array effects, and EMC/EMI associated with plasma/neutral gas operations. The Space Station and its associated systems pose unique demands on the ability to simulate these effects; synergistic effects require multiple environments to be simulated simultaneously, and the long life requirements require proper scaling of the exposure time. The analysis of specific effects and the calibration or improvement of ground test techniques will likely require in situ evaluation. Qualification and acceptance testing, because of cost and the impractically of extensive on-orbit analysis/modification, will likely remain ground test objectives except in very rare cases.

Garrett, Henry B.↗